In the art, different methods are known suitable for application of treatment agents (chemicals) on a web in a paper machine or similar equipment. For instance, an embodiment has been disclosed with an objective to aid the takeoff of the paper web from the intermediate roll of the paper machine press section by means of dosing a web release agent into the lubrication spray of the press roll doctor element. The desired goal of this arrangement is to facilitate a portion of the added agent to pass into the nip between the doctor element and the press roll, therein forming a film on the roll surface. The function of the film formed by the chemical additive is to aid the takeoff of the web from the roll surface by virtue of, e.g., lowering or increasing the surface tension of water, depending on the composition of the agent used. Among other disadvantages, this prior-art embodiment is handicapped by the following drawbacks. When operating properly, the doctor element cleans the roll surface free from all water, deposits and possible residues of the chemical additive so effectively that the roll surface after doctoring will be dry with no film of the chemical additive remaining thereon. The effect of the chemical will be minimal and the chemical losses high. By contrast, if the chemical is allowed to pass through the nip between the doctor element and the roll, the unavoidable corollary is that the doctoring effect must be reduced, whereby web breaks and production losses will be encountered in the paper mill. Broadly, conventional application methods misuse the potential effect of chemical additives and frequently involve excessive consumption of the chemical.
It is an object of the present invention to provide an entirely novel arrangement for application of a variety of web treatment agents (chemicals) in a paper or paperboard machine. The goal of the invention is achieved by virtue of dosing the treatment chemical into the stream of a carrier gas such as steam and then applying the stream directly to the web surface via gas stream applicator device such as a steam box.